A Strange Tale

The hind end of a sauropod dinosaur was an amazing structure. Imagine a tail as long as a school bus. Now imagine that it weighs as much as three grand pianos. Finally, imagine that it's as big as a trash can at one end and as small as a pencil at the other. Congratulations! You've just visualized the rear third of Apatosaurus!

What accounts for this striking shape? Did tails counterbalance those impossibly long necks? Did sauropods use their tails to steady themselves when--or if--they occasionally reared up? Tails may also have had another, more surprising role, as noisemakers. Some scientists think the animals snapped them like whips.

Iguana.

Corbis

A Surprise Ending

Diplodocids had a series of thickened, conical scales running the length of its back from head to tail. Modern iguanas have a similar structure.

Tapering Off

Every sauropod tail combined very different types of bones. They ranged from small rodlike vertebrae at the tip to huge, complex structures near the animal's hindquarters, such as a tailbone from the sauropod Diplodocus.

The structures that jut from the top provided added surface area for attachment of the huge muscles and ligaments. Powerful muscles may have allowed Diplodocus to swing its tail quickly. Projections get smaller in the direction of the tip, indicating most of the animal's tail muscles were close to its body.

A triangular bone, called a chevron, comes from the underside of Apatosaurus's tail and provided further muscle support.

Coiled to Strike?

14 rod-shaped bones are part of the tip of a sauropod tail. Though all sauropods had long tails, only those of the diplodocids, including Diplodocus and Apatosaurus, ended in whiplike tips. Those animals had 73 and 82 tail bones, respectively.

The tail was found in the bent position, making its resemblance to a whip even more striking. This similarity led early researchers to speculate that diplodocids used their tails for slashing predators.